This summer, I've been reading articles about how residents of Barcelona (Spain), Dubrovnik (Croatia) and Venice (Italy) have been pushing back at group tours, cruise ships and fans of television shows wanting to see the cities in which the shows are filmed.

Here's a very long article detailing what has been the flipside of tourism for residents-it's hard to live at home when the crowds are there all the time.

For residents of Porto, however, the bookstore has a different story to tell. It is one of economic upswing in a country that was in the throes of crisis not all that long ago. Indeed, Portugal owes its recovery in part to double-digit growth in tourism, including in the areas in the once impoverished north around Porto. Ryanair and EasyJet have been flying to the city for years, and it has long been regarded as the new in-spot for city-escape tourism. Last year, around 2.5 million foreign tourists visited the region, and half of them visited Livraria Lello. Porto still hasn't become as overrun as places like Barcelona or Amsterdam, cities where locals have begun defending themselves against the hordes of tourists who seem to be taking over. But a divide has developed in Porto -- between the tourist city and the city for locals. One can't help but wonder when a local last visited Livraria Lello. Do Porto residents also have to stand in line and pay five euros?

In many places, that feeling has begun manifesting itself in expressions of open hostility. Activists spray paint "tourists go home" on the walls in many places overflowing with tourists, and in Mallorca, they even proclaimed a "summer of action," with protests against travelers at the airport and in hotels. In Palma, activists have thrown horse droppings at tourists. In Barcelona they have pushed people from bicycles and harassed them in cafés. In Venice, self-proclaimed pirates have taken the dramatic step of blocking cruise ships from entering the port.